This invention relates to proteins characterized by the ability to selectively inhibit T-cell mediated immune responses.
U.S. Pat. No. 4,665,032 issued May 12, 1987 and an article by Laurence et al Immunoreoulatory Lymohokines of T-Hybridomas from AIDS Patients: Constitutive and Inducible Suppressor Factors (Science, 6th, Jul., 1984, Vol. 225, pgs. 66-69) together disclose the existence of an immune response suppressor activity originally discovered in lectin-free cultures of peripheral blood mononuclear cells from AIDS patients. The patent discloses the preparation of T-cell hybridoma cell lines which can be cultured as a source of the active protein called "soluble suppressor factor" or SSF. The putative protein differs significantly in its physiological effects from various other materials classed as soluble suppressor factors (see, e.g., Soluble Immunosuppressor Factors in Human Cancer, Guidi et al., Clinical Immunology Newsletter 9:8, 1988, pg. 124) in that it selectively inhibits T-cell dependent immune responses. A pharmaceutical grade source of this new SSF would be useful in the management of disorders requiring immunosuppression such as autoimmune diseases, hypersensitivity reactions, and organ allografting procedures. However, despite the availability of continuous cell lines which secrete the suppressor factor, and therefore necessarily contains messenger RNA encoding it, determination of the primary structure of the protein has eluded the art.
It is an object of the invention to provide soluble suppressor factors, including native form materials, muteins, truncated analogs, fusion proteins, and other constructs, capable of specifically inhibiting T-cell immune responses in humans and other mammals. Another object is to provide DNA encoding the active region of a protein capable of inhibiting selectively human T-cell immune responses.